A lithium mixed metal oxide is used as a cathode active material for non-aqueous electrolyte secondary batteries such as lithium secondary batteries. Lithium secondary batteries have been already put into practical use as an electrical source of cellular telephones, notebook computers and the like, and further, tried to be applied in middle size and large size applications such as an automobile application, electric power storage application and the like.
As lithium mixed metal oxides used for cathode active materials of conventional lithium secondary batteries, JP-A No. 2002-100356 (Example 6) discloses a lithium-nickel-manganese-cobalt mixed oxide, and specifically discloses LiNi0.45Mn0.45Co0.1O2 prepared by adding an alkali aqueous solution to a mixed aqueous solution of nickel sulfate, manganese sulfate and cobalt sulfate to induce co-precipitation, calcining the resultant co-precipitated hydroxide in an atmosphere at 550° C., further mixing lithium carbonate, and calcining the mixture in a nitrogen gas at 800° C.
However, as to lithium secondary batteries containing conventional cathode active material, the capacity retention in a charge and discharge cycle test is not sufficient. The present invention has an object of providing a lithium mixed metal oxide useful for non-aqueous electrolyte secondary batteries, which can show high capacity retention.